That sounds like the ECU is going into Fail Safe Operation. The ECU has self diagnostics and when it detects a problem it goes into 1 of 2 modes. If it detects an error with the Ignition Pulse Generator, Cam Position Sensor, or the Injectors, the ECU will just shut the engine down and will not restart or engage the fuel pump. Any of the other sensors like TPS, OS, MAP, ECT and others will cause it to go into Fail Safe Operation. This allow the engine to limp home with reduced power and be ridden to a shop. You're going to need to check the operation of each of the various sensors and especially connection to them and verify their operation. I'd suggest you find a copy of the shop manual as it explains how to check all those sensors. It's not going to be a quick fix most likely.